The relevant components in a typical prior art magnetic storage device (disk drive) 10 are illustrated in FIG. 1 in simplified block form. Although only one disk 16 and one slider 11 are shown, there may be multiple disks in a drive and typically there are two sliders per disk, i.e., one for each surface of the disk. This disk drive comprises a thin film magnetic disk 16 for recording data, a slider 11 that carries out the reading and writing of data in tracks on the magnetic disk 16. An arm electronics (AE) module 17 has circuits that, among other functions, provide bias for read head (not shown) and amplify the signals from the read head. The arm electronics (AE) module 17 is controlled by a read/write (R/W) channel 18 that carries out the reading of servo sectors and the reading and writing of data. A rotary actuator 12 moves the arm 22 and the attached slider 11 in an arcuate path approximately along a radius of the magnetic disk 16 to read and write data in circular tracks around the disk as the disk is being rotated by a spindle motor (not shown) which rotates spindle 24. The direction of rotation is shown with the slider and arm pointing in the direction of rotation, i.e., a selected point on the rotating disk first passes under the arm 22, then passes under the slider 11. This orientation between the arm/slider and the direction of rotation causes the air-bearing to form and will be referred to as the forward or operational direction. The operational direction can be clockwise as shown in FIG. 1 or it can be counterclockwise in which case the arm/slider would appear on the opposite side of the spindle 24. The operational direction is fixed by the design of the drive. The drive 10 includes a load/unload ramp structure 26 which lifts the arm to in turn lift the slider off of the disk when the arm is rotated out to the outer diameter (OD). A crash-stop 28 prevents the arm from rotating too close to the spindle. A spindle motor driver 14 under the direction of the hard disk controller (HDC) 20 controls the direction and speed of rotation. The spindle motor driver 14 includes circuitry that drives the coils of the spindle motor individually and thereby has highly flexible control over the spindle motor. The HDC 20 is a programmable device which executes instructions stored in the program in memory 19. The microprocessor unit (MPU) 21 has a processor, memory, an interface to external apparatus, and the like, and controls communication with the host apparatus (not shown).
FIG. 2 illustrates a partial section of a particular embodiment of a slider 11 having a write head 11W and a read head 11R. The read head 11R reads magnetic transitions as the disk rotates under the air-bearing surface (ABS) of the slider 11. The view is at the point in the fabrication when the wafer has been sawed along the line labeled “ABS” and before any of the air-bearing features or the overcoat has been fabricated. The components of the read head 11R are the first shield (S1), two insulation layers 107, 109 which surround the sensor element 105 (also called the MR-stripe) and the second shield 101 (P1/S2). The MR-stripe can be composed of a single layer or of multiple layers of varying materials. The term “stripe height” refers to the dimension of the sensor element 105 measured from the ABS to the opposite end of the element. Controlling the stripe height is important for the response of the read head to magnetic fields originating in the thin films on the disk. This type of slider is called a “merged head” because the P1/S2 layer 101 serves as a shield for the read head 11R and a pole piece for the write head 11W. The yoke also includes another pole piece P3103 which connects with P1/S2101. The P2102 confronts the P1/S2101 across the write gap layer 43 to form the write gap at the air-bearing surface (ABS). The zero throat height (ZTH) is defined as the distance from the ABS to the point where the P3 separates from the gap layer by forming a step on the gap layer 43. Control over the ZTH is one of the limitations encountered when attempts are made to reduce the track width of this type of write head 11W. One technique for controlling the ZTH and the stripe height is to make the cut slightly beyond where the final ABS should be and then the lap the ABS to precisely remove material until the desired plane is reached.
In the typical manufacturing process for sliders 11 for magnetic storage devices 10, a large number of sliders are fabricated from a single wafer having rows and columns of the magnetic transducers which are deposited simultaneously on the wafer surface using semiconductor-type process methods. In various process embodiments, further processing must occur after the wafer is sliced into rows or individual sliders to expose the transducer elements. The sliders are then processed to form the protective layers and air-bearing surface features. Typically, a slider is formed with an aerodynamic pattern of protrusions (air-bearing features) on the air-bearing surface (ABS) which enable the slider to fly at a constant height close to the disk during operation of the disk drive. The recording density of a magnetic disk drive is limited by the distance between a transducer and the magnetic media. One goal of air-bearing slider design is to “fly” as closely as possible to the magnetic medium while avoiding excessive physical impact with the medium. Smaller spacing or “fly height” is desired so that the transducer can distinguish between the magnetic fields emanating from closely spaced regions on the disk. After all of the features have been formed each slider has a read and write head terminating at the ABS covered by an overcoat layer which is commonly a carbon-based material.
The manufacturing process for magnetic disks 16 for use in disk drives typically includes burnishing using a special burnishing head. Published U.S. patent application 2002/0029448 describes this process and includes a description of a burnishing head. This burnishing during manufacturing of the disk is to be distinguished from burnishing which can be performed after the disk is installed in the drive. In U.S. Pat. No. 6,419,551 to G. Smith burnishing in a completed disk drive is achieved by the use of an external vacuum source which is applied to the disk drive to lower the flying height of the slider below the operational level even though the rotational rate has been increased. For disk drives being operated in normal customer environments a vacuum source is not available, so lowered rotational speed can be used to lower the flying height and burnish high spots on the disk. One described burnishing scheme uses heat generated by the electrical components in magnetic transducer to cause a physical protrusion at the rear of the slider to accomplish disk burnishing.
A process of burnishing so-called “textured disks” has been described by P. CALCAGNO, et al., in “Reverse Process Burnishing Method for Disk Surfaces”, IBM Technical Disclosure Bulletin, 02-1994, vol. 37 no. 02A. They note that the texturing process, which involves rotating the disk while an abrasive material or surface is held against the disk surface, tends to leave burrs on the back side of the texture grooves. If the burnishing process is performed with the disk rotating in the opposite direction from that used for texturing, the burrs will tend to be folded into the grooves and, therefore, made less obtrusive. It should be noted that the rotational direction for texturing and burnishing in this context have no relationship to the direction that the disk will be rotated in when installed in a disk drive.
Burnishing can also be performed on the slider 11 after it is installed in a drive. For example, U.S. Pat. No. 6,493,184 to G. Smith describes a disk design which includes dedicated burnishing zones that are rougher than the rest of the disk and can be used to burnish the slider in a disk drive.
In order to improve performance of magnetic storage devices, there is a need for improved methods of burnishing sliders.